Is baking soda fizzing when mixed with vinegar a physical or chemical change?

It is a chemical reaction. Baking soda contains carbonate ions, which react with hydrogen ions from the acetic acid in vinegar according to the ionic equation:

CO3-2 + 2 H+ -> CO2 + H2O. CO2 is a gas at standard temperature and pressure. CO2 formation causes the fizzing, as the gas escapes from the other product and the still unreacted baking soda and vinegar.

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Well, you completely deleted my very simple and responsive answer and made it a little more complicated.

As I said in my first response, this is a chemical reaction involving the combination of an acid and a base. When an acid and base combine, the reaction easily moves forward forming a salt. This is a chemical reaction. I should have also added that the byproducts were also included water and CO2 and perhaps some unreacted original products depending upon the amount of each supplied.

Along the lines of your response a more complete response would be:

CH3COOH + Na(HCO3) -> H2O + NaOCOCH3 + CO2

vinegar is mostly a weak acetic acid - CH3COOH and water.

baking soda is essentially - Na(HCO3)

The sodium precipitate on the right side is the residue I was speaking of. It is by definition, a salt.

(You shouldn't have erased my answer because it wasn't wrong and completely responsive to the question. I rather doubt the person making the query wanted to know THAT much about it. Now you want to balance this equation for everyone?)